Catalyst having a ketimide ligand

ABSTRACT

A catalyst system comprises an organometallic complex of a group 4 metal having a ketimide ligand. The organometallic complex preferably also contains a cyclic ligand which forms a delocalized pi-bond with the metal (such as a cyclopentadienyltype ligand). Preferred organometallic complexes may be activated with a so-called “substantially non coordinating anion” to form a low cost cocatalyst system which is excellent for the preparation of olefin copolymers having both high molecular weight and very low density.

This is a division of application Ser. No. 09/140,608, filed Aug. 26,1998 U.S. Pat. No. 6,114,481.

FIELD OF THE INVENTION

This invention relates to a catalyst system for the preparation ofolefin copolymers. The catalyst system is especially useful for thepreparation of ethylene copolymers which have very high molecular weightand very low density. The catalyst system is characterized by the use ofan organometallic complex having a ketimide ligand.

BACKGROUND OF THE INVENTION

Ketimide complexes of group 4 metals have been reported in theliterature—see, for example, the review of titanium chemistry which asprepared in part by one of us in 1982 (Ref: M. Bottrill, P. D. Gavens,J. W. Kelland and J. MeMeeking in “Comprehensive OrganometallicChemistry”, Ed. G. Wilkinson, F. G. A. Stone, & E. W. Abel, PergamonPress, 1982, Section 22.3, page 392). However, the use of ketimideligand/group 4 metal complex as an ethylene polymerizafion catalyst washeretofore unknown.

Preferred ketimide catalysts of this invention also contain one and onlyone cyclopentadienyl-type ligand.

The prior art includes many examples of olefin polymerization catalystshaving a single cyclopentadienyl ligand—most notably the so calledBercaw ligand (*Cp-Me₂Si—N^(t)Bu) which was disclosed as a Scandiumcomplex by Bercaw et al In the fall of 1988 and subsequently claimed asa titanium complex in U.S. Pat. No. 5,064,802 (Stevens and Neithamer, toDow Chemical) and U.S. Pat. No. 5,055,438 (Canich, to Exxon). The use ofa titanium complex of the Bercaw ligand provides an olefinpolymerization catalyst which has excellent commoner response—i.e. thecatalyst Is excellent for the preparation of ethylene/α-olefincopolymers. However, the bridged structure of the Bercaw ligand isexpensive to synthesize. Accordingly, an olefin polymerization catalystwhich doesn't require a “bridge” to provide commoner response wouldrepresent a useful addition to the art.

SUMMARY OF THE INVENTION

The present invention also provides a catalyst system for olefinpolymerization comprising;

(a) a catalyst which is an organometallic complex of a group 4 metal;and

(b) an activator, characterized in that such organometallic complexcontains a ketimide ligand.

Preferred forms of the catalyst contain a single ketimide ligand and asingle cyclopentadienyl-type ligand.

The invention further provides a process for the copolymerization ofethylene with at least one other olefin monomer using the abovedescribed catalyst system.

DETAILED DESCRIPTION

The term “group 4” metal refers to conventional IUPAG nomenclature. Thepreferred group 4 metals are Ti, Hf and Zr with Ti being most preferred.

As used herein, the term “ketimide ligand” refers to a ligand which:

(a) is bonded to the group 4 metal via a metal-nitrogen atom bond,

(b) has a single substituent on the nitrogen atom, (where this singlesubstituent Is a carbon atom which is doubly bonded to the N atom); and.

(c) has two substituents (Sub 1 and Sub 2, described below) which arebonded to the carbon atom.

Conditions a, b, and c are illustrated below:

The substituents “Sub 1 and Sub 2” may be the same or different.Exemplary substituents include hydrocarbyls having from 1 to 20 carbonatoms; silyl groups, amido groups and phosphido groups. For reasons ofcost and convenience it is preferred that these substituents both behydrocarbyls, especially simple alkyls and most preferably tertiarybutyl.

In the preferred catalyst systems, the catalyst is defined by theformula:

L₁L₂MX₂  formula 1

L2:

L2 is a cyclic ligand which forms a delocalized pi-bond with the group 4metal. L2 is preferably a cyclopentadienyltype ligand.

As used herein, the term cyclopentadienyl-type is meant to convey itsconventional meaning and to include indenyl and fluorenyl ligands. Thesimplest (unsubstituted) cyclopentadione indeno and fluorene structuresare illustrated below.

Ligands in which one of the carbon atoms in the ring is replaced with aphosphorous atom (i.e. a phosphole) may also be employed

It will be readily appreciated by those skilled in the art that thehydrogen atoms shown in the above formula may be replaced withsubstituents to provide the “substituted” analogues, Thus, the preferredcatalysts contain a cyclopentadienyl structure which may be anunsubstituted cyclopentadienyl, substituted cyclopentadienyl,unsubstituted indenyl, substituted indenyl, unsubstituted fluorenyl orsubstituted fluorenyl. A description of permissible substituents onthese cyclopentadienyl-type structures is provided in U.S. Pat. No.5,324,800 (Welbom).

An illustrative list of such substituents for cyclopentadienyl groupsincluded C₁-C₂₀ hydrocarbyl radicals; substituted C₁-C₂₀ hydrocarbylradicals wherein one or more hydrogen atoms is replaced by a halogenradical, an amido radical, a phosphido radical, an alkoxy radical or aradical containing a Lewis acidic or basic functionality; substitutedC_(1-C) ₂₀ hydrocarbyl radicals wherein the substituent contains an atomselected from the group 14 of the Periodic Table of Elements (wheregroup 14 refers to IUPAC nomenclature); and halogen radicals, amidoradicals, phosphido radicals, alkoxy radicals, alkyborido radicals, or aradical containing Lewis acidic or basic functionality; or a ring inwhich two adjacent R-groups are joined forming C_(1-C) ₂₀ ring to give asaturated or unsaturated polyclinic ligand.

Ligand X: “Non-Interfering Anionic Ligand”

Referring for formula 1, the preferred catalyst systems according tothis invention contain two simple anionic ligands denoted by the letterX.

Any simple anionic ligand which may be bonded to an analogousmetallocene catalyst component ((i.e. where the analogous metallocenecatalyst component is defined by the formula Cp₂M(X)₂, where Cp is acyclopentadienyl-type ligand; M Is a group 4 metal; and X is anon-interfering ligand Is previously defined herein) may also be usedwith the catalyst components or this invention.

“Non-interfering” means that this ligand doesn't interfere with(deactivate) the catalyst.

An Illustrative list includes hydrogen, hydrocarbyl having up to 10carbon atoms, halogen, amido and phosphido (with each X preferably beingchlorine, for simplicity).

Polymerization Details

The polymerization process of this invention is conducted in thepresence of a catalyst and an “activator or cocatalyst”. The terms“activator” or “cocatalyst” may be used interchangeably and refer to acatalyst component which combines with the organometallic complex toform a catalyst system that is active for olefin polymerization.

Preferred cocatalysts are the well know alumoxane (also known asaluminoxane) and ionic activators.

The term “alumoxane” refers to a well known article of commerce which istypically represented by the following formula:

R₂′AlO(R′AlO)_(m)AlR₂′

were each R′ is independently selected from alkyl, cycloalkyl, aryl oralkyl substituted aryl and has from 1-20 carbon atoms and where m isfrom 0 to about 50 (especially from 10 to 40). The preferred alumoxaneis methylalumoxane or “MAO” (where each of the R′ is methyl).

Alumoxanes are typically used in substantial molar excess compared tothe amount of metal in the catalyst. Aluminum:transition metal molarratios of from 10:1 to 10,000:1 are preferred, especially from 50:1 to500:1.

Another type of activator is the “ionic activator” or “substantiallynon-coordinating anion”. As used herein, the term substantiallynon-coordinating anions (“SNCA”) well known cocatalyst or activatorsystems which are described, for example, in U.S. Pat. No. 5,153,157(Hlatky and Turner), and the carbonium, sulfonium and oxonium analoguesof such activators which are disclosed by Ewen in U.S. Pat. No.5.387.568. In general, these SNCA form an anion which only weaklycoordinates to a cationic form of the catalyst.

While not wanting to be bound by theory, it is generally believed thatSNCA-type activators ionize the catalyst by abstraction or protonationof one of the “X” ligands (non-interfering ligands) so as to ionize thegroup 4 metal center into a cation (but not to covalently bond with thegroup 4 metal) and to provide sufficient distance between the ionizedgroup 4 metal and the activator to permit a pulverizable olefin to enterthe resulting active site. It will appreciated by those skilled in theart that it is preferable that the “non-interfering”(“X”) ligands besimple alkyls when using a SNCA as the activator. This may be achievedby the alkylation of a halide form of the catalyst.

Examples of compounds capable of ionizing the group 4 metal complexinclude the following compounds:

triethylammonium tetra(phenyl)boron,

tripropylammonium tetra(phenyl)boron,

tri(n-butyl)ammonium tetra(phenyl)boron,

trimethylammonium tetra(p-tolyl)boron,

trimethylammonium tetra(o-tolyl) boron,

tributylammonium tetra(pentafluorophenyl)boron,

tripropylammonium tetra(o,p-dimethylphenyl)boron,

tributylammonium tetra(m,m-dimethylphenyl)boron,

tributylammonium tetra(p-trifluoromethylphenyl)boron,

tribulylammonium tetra(pentafluorophenyl)boron,

tri(n-butyl)ammonium tetra(o-tolyl)boron,

N,N-dimethylanilinium tetra(phenyl)boron,

N,N-diethylanilinium tetra(phenyl)boron,

N,N-diethylanilinium tetra(phenyl)n-butylboron,

N,N-2,4,6-pentamethylanilinium tetra(phenyl)boron,

di-(isopropyl)ammonium tetra(pentafluorophenyl)boron,

dicyclohexylammonium tetra(phenyl)boron,

triphenylphosphonium tetra(phenyl)boron,

tri(dimethylphenyl)phosphonium tetra(phenyl)boron,

tri(dimethylphenyl)phosphonium tetra(phenyl)boron,

tropillium tetrakispentafluorophenyl borate,

triphenylmethylium tetrakispentafluorophenyl borate,

benzene (diazonium) tetrakispentafluorophenyl borate,

tropillium phenyltris-pentafluorophenyl borate,

triphenylmethylium phenyl-trispentafluorophenyl borate,

benzene (diazonium) phenyltrispentafluorophenyl borate,

tropillium tetrakis(2,3,5,6-tetrafluorophenyl) borate,

triphenylmethylium tetrakis(2,3,5,6-tetrafluorophenyl) borate,

benzene (diazonium) tetrakis(3,4,5-trifluorophenyl) borate,

tropilliurm tetrakis(3,4,5-trifluorophenyl) borate,

benzene (diazonium) tetrakis(3,4,5-trifluorophenyl) borate,

tropillium tetrakis(1,2,2-trifluoroethenyl) borate,

triphenylmethylium tetrakis(1,2,2-trifluoroethenyl) borate,

benzene (diazonium) tetrakis(1,2,2-trifluoroethenyl) borate,

tropillium tetrakis (2,3,4,5-tetrafluorophenyl) borate,

triphenylmethylium tetrakis(2,3,4,5-tetrafluorophenyl)

borate, and

benzene (diazonium) tetrakis(2,3,4,5-tetrafiuorophenyl) borate.

Readily commercially available activators which are capable of ionizingthe group 4 metal complexes include;

N,N-dimethylaniliumtetrakispentafluorophenyl borate

(“[Me₂NHPh][B(C₆F₅)₄]”); and

triphenylmethylium tetrakispentafluorophenyl borate(“[Ph₃C][B(C₆F₅)₄]”); and

trispentafluorophenyl boron.

These SNCA activators are typically used in approximately equimolaramounts (based on the group 4 metal in the catalyst) but lower levelsmay also be successful and higher levels also generally work (thoughsub-optimally with respect to the cost-effective use of the expensiveactivator).

In addition to the catalyst and cocatalyst, the use of a “poisonscavengers” may also be desirable. As many be inferred from the name“poison scavenger”. these additives may be used in small amounts toscavenge impurities in the polymerization environment. Aluminum alkyls,for example trisobutyl aluminum, are suitable poison scavengers. (Note:some caution must be exercised when using poison scavengers as they mayalso react with, and. deactivate, the catalyst.)

Polymerizations according to this invention may be undertaken in any ofthe well know olefin polymerization processes including those known as“gas phase”, “slurry”, “high pressure” and “solution”.

The use of a supported catalyst is preferred for gas phase and slurryprocesses whereas a non-supported catalyst is preferred for the solutionprocess.

When utilizing a supported catalyst, it may be preferable to initiallysupport the cocatalyst, then the catalyst (as will be illustrated in theExamples).

The polymerization process according to this invention uses ethylene andmay include other monomers which are copolymerizable therewith (such asother alpha olefins, preferably butene, hexene or octene, and undercertain conditions, dienes such as hexadiene isomers, vinyl aromaticmonomers such as styrene or cyclic olefin monomers such as norbornene).

The present invention may also be used to prepare elastomeric co- andterpolymers of ethylene, propylene and optionally one or more dienemonomers. Generally. such elastomeric polymers will contain about 50 toabut 75 weight % ethylene, preferably about 50 to 60 weight % ethyleneand correspondingly from 50 to 25 % of propylene. A portion of themonomers, typically the propylene monomer, may be replaced by aconjugated diolefin. The diolefin may be present in amounts up to 10weight % of the polymer although typically is present in amounts fromabout 3 to 5 weight %. The resulting polymer may have a compositioncomprising from 40 to 75 weight % of ethylene, from 50 to 15 weight % ofpropylene and up to 10 weight % of a diene monomer to provide 100 weight% of the polymer. Preferred but not limiting examples of the dienes aredicyclopentadliene, 1,4-hexadiene, 5-methylene-2-norbornene,5-ethylidene-2-norbornene and 5-vinyl-2-norbornene. Particularlypreferred dienes are 5-ethylidene-2-norbornene and 1,4-hexadiene.

The polyethylene polymers which may be prepared in accordance with thepresent invention typically comprise not less than 60, preferably notless than 70 weight % of ethylene and the balance one or more Cr₄₋₁₀alpha olefins, preferably selected from the group consisting of1-butene, 1-hexene and 1-octene. The polyethylene prepared in accordancewith the present invention may be linear low density polyethylene havingdensity from about 0.910 to 0.935 g/cc. The present invention might alsobe useful to prepare polyethylene having a density below 0.910 g/cc—theso called very low and ultra low density polyethylenes.

The most preferred polymerization process of this invention encompassesthe use of the novel catalysts (together with a cocatalyst) in a mediumpressure solution process. As used herein, the term “medium pressuresolution process” refers to a polymerization carried out in a solventfor the polymer at an operating temperature from 100 to 320° C.(especially from 120 to 220° C.) and a total pressure of from 3 to 35mega Pascals. Hydrogen may be used in this process to control (reduce)molecular welgnt. Optimal catalyst and cocatalyst concentrations areaffected by such variables as temperature and monomer concentration butmay be quickly optimized by non-inventive tests.

Further details concerning the medium pressure polymerization processare well known lo those skilled in the art and widely described in theopen and patent literature.

The catalyst of this invention may also be used in a slurrypolymerization process or a gas phase polymerization process.

The typical slurry polymerization process uses total reactor pressuresof up to about 50 bars and reactor temperature of up to about 200° C.The process employs a liquid medium (e.g. an aromatic such as toluene oran alkane such as hexane, propane or isobutane) In which thepolymerization take place. This results in a suspension of solid polymerparticles in the medium. Loop reactors are widely used in slurryprocesses. Detailed descriptions of slurry polymerization processes arewidely reported in the open and patent literature.

In general, a fluidized bed gas phase polymerization reactor employs a“bed” of polymer and catalyst which is fluidized by a flow of monomerwhich is at least partially gaseous. Heat is generated by the enthalpyof polymerization of the monomer flowing through the bed. Unreactedmonomer exits the fluidized bed and is contacted with a cooling systemto remove this heat. The cooled monomer is then re-circulated throughthe polymerization zone together with “make-up” monomer to replace thatwhich was polymerized on the previous pass As will be appreciated bythose skilled in the art, the “fluidized” nature of the polymerizationbed helps to evenly distribute/mix the heat of reaction and therebyminimize the formation of localized temperature gradients (or “hotspots”). Nonetheless, it is essential that the heat of reation beproperly removed so as to avoid softening or melting of the polymer (andthe resultant-and highly undesirable—“reactor chunks”). The obvious wayto maintain good mixing and cooling is to have a very high monomer flowthrough the bed. However, extremely high monomer flow causes undesirablepolymer entrainment.

An alternative (and preferable) approach to high monomer flow is the useof an inert condensable fluid which will boil in the fluidized bed (whenexposed to the enthalpy of polymerization), then exit the fluidized bedas a gas, then come into contact with a cooling element which condensesthe inert fluid. The condensed, cooled fluid is then returned to thepolymerization zone and the boiling/condensing cycle is repeated.

The above-described use of a condensable fluid additive in a gas phasepolymerization is often referred to by those skilled in the art as“condensed mode operation” and is described in additional detail in U.S.Pat. No. 4,543,399 and U.S. Pat No. 5,352,749. As noted in the '399reference, it is permissible to use alkanes such as butane, pentanes orhexanes as the condensable fluid and the amount of such condensed fluidpreferably does not exceed about 20 weight per cent of the gas phase.

Other reaction conditions for the polymerization of ethylene which arereported in the '399 reference are: Preferred PolymerizationTemperatures: about 75° C. to about 115° C. (with the lower temperaturesbeing preferred for lower melting copolymers—especially those havingdensities of less than 0.915 g/cc—and the higher temperatures beingpreferred for higher density copolymers and homopolymers); and Pressure:up to abut 1000 psi (with a preferred range of from about 100 to 350 psifor olefin polymerization).

The '399 reference teaches that the fluidized bed process is welladapted for the preparation of polyethylene but further notes that othermonomers may also be employed. The present invention is similar withrespect to choice of monomers.

Catalysts which are used in gas phase and slurry polymerizations arepreferably supported. An exemplary list of support materials includemetal oxides (such as silica, alumina, silica-alumina, titania andzirconia); metal chlorides (such as magnesium chloride); talc, polymers(including polyolefins); partially prepolymerized mixtures of a group 4metal complex, activator and polymer; spray dried mixtures of the group4 metal complex, activator and fine “inert” particles (as disclosed, forexample, in European Patent Office Application 668,295 (to UnionCarbide).

The preferred support material is silica. In a particularly preferredembodiment, the silica has been treated with an alumoxane (especiallymethylalumoxane or “MAO”) prior to the deposition of the group 4 metalcomplex. The procedure for preparing “supported MAO” which is describedin U.S. Pat. No. 5,534,474 (to Wltco) may provide a low cost catalystsupport. It will be recognized by those skilled in the art that silicamay be characterized by such parameters as particle size, pore volumeand residual silanol concentration. The pore size and silanolconcentration may be altered by heat treatment or calcining. Theresidual silanol groups provide a potential reaction site between mealumoxane and the silica (and, indeed, some off gassing is observed whenalumoxane is reacted with silica having residual silanol groups). Thisreaction may help to “anchor” the alumoxane to the silica (which, inturn, may help to reduce reactor fouling).

The preferred particle size, preferred pore volume and preferredresidual silanol concentration may be influenced by reactor conditions.Typical silicas are dry powders having a particle size of from i to 200microns (with an average particle size of from 30 to 100 beingespecially suitable); pore size from 50 to 500 Angstroms; and porevolumes of from 0.5 to 5.0 cubic centimeters per gram. As a generalguideline, the use of commercially available silicas, such as those soldby W. R. Grace under the trademarks Davison 948 or Davison 955, aresuitable.

EXAMPLES

The invention will now be illustrated in further detail by way of thefollowing non-limiting examples. For clarity, the Examples have beendivided into two parts, namely Part A (Catalyst Component Synthesis),Part B (Solution Polymerization) and Part C (Gas Phase Polymerization).

Polymer Analysis

Gel permeation chromatography (“GPC”) analysis was carried out using acommercially available chromatograph (sold under the name Waters 150GPC) using 1,2,4-trichlorobenzene as the mobile phase at 140° C. Thesamples were prepared by dissolving the polymer in the mobile phasesolvent in an external oven at 0.1% (weight/volume) and worn run withoutfiltration. Molecular weights are expressed as polyethylene equivalentswith a relative standard deviation of 2.9% and 5.0% for the numberaverage molecular weight Mn and weight Mw, respectively. Melt index (MI)measurements were conducted according to ASTM method D-1238-82.

Polymer densities were measured using pressed plaques (AST D-1928-90),with a densitometer. The polymer composition was determined using FTIRwhere the 1-butane or 1-hexone content was measured.

Part A: Catalyst Component Synthesis

Experimental Section

Catalyst components were prepared using conventional organometallicsynthetic techniques, as described below.

Preparation of ^(t)Bu₂C═NLi (where ^(t)Bu is tertiary butyl, and ^(t)Bu₂shows that two tertiary butyl groups are bonded to the C (carbon) atom)

This compound was prepared according to a published procedure, D.Armstrong, D. Barr and R. Sanith J. Chem. Soc. Dalton Trans. 1987, 1071.¹H NMR (proton nuclear magnetic resonance) (toluene-d₈₁δ): 1.21 (s).

Synthesis of (^(t)Bu₂C═N)TiCl₂Cp (where Cp is a cyclopentadienyl ligand)

A solution of ^(t)Bu₂C═NLI (1.34 g, 9.11 mmol) in toluene (˜20 mL. i.e.approximately 20 mL) was added slowly to CpTiCl₃ (2.0 g, 9.11 mmol) intoluene (˜30 mL) at −78° C. The yellow solution became orangeimmediately. The reaction mixture was warmed to 23° C. in 12 hours. Thereddish purple solution was filtered through a fine glass filter toremove LiCl and the filtrate was pumped to ˜5 mL and hexane (˜40 mL) wasadded. The product crystallized at −70° C. as purple crystals (2.4 g).Evaporation of the mother liquor in a glove box gave X-ray qualitycrystals (extra 0.3 g). The combined yield was 91%. ¹H NMR(toluene-d₈₁δ): 6.12 (s, 5H), 1.04 (s, 18H).

Synthesis of (^(t)Bu₂C═N)TiMe₂Cp (where Me is methyl)

MeMgBr (3M in ether, 1.1 mL, 3.3 mmol) was added to a toluene solution(40 mL) of (^(t)Bu₂C═N)TiCl₂Cp (0.416 g, 1.283 mmol) at −78° C. Afterthe addition, the solution was warmed to 23° C. in 30 minutes and wasthen pumped to dryness. The residue was extracted with hexane (2×35 mL)and the slurry was filtered. The filtrate was pumped to dryness to givethe pure product as an orange oil. ¹H NMR (toluene-d₈₁δ) 6.0 (s, 5H),1.15 (s, 18H). 0.636 (s, 6H).

Synthesis of (^(t)Bu₂C═N)TiCl₂Cp* (where Cp* ispentamethylcyclopentadienyl)

Analogous to the synthesis of (^(t)Bu₂C═N)TiCl₂Cp, this compound wassynthesized from ^(t)Bu₂C═NLi and Cp*TiCl₃ as orange crystals in almostquantitative yield. ¹H NMR (toluene-d₈₁δ): 1.976 (s, 15H), 1.15 (s,18H).

Synthesis of (^(t)Bu₂C═N)TiMe₂Cp*

Analogous to the synthesis of (^(t)Bu₂C═N)TiMe₂Cp, this compound wasprepared from MeMgBr and (^(t)Bu₂C═N)TiCl₂Cp* as orange crystals inquantitative yield. ¹H NMR (toluene-d₈₁δ): 1.889(s,15H), 1.219 (s, 18H),0.446 (s, 6H).

Synthesis of [(Me₂N)₂C═N]TiCl₂Cp

BuLi (1.6 M in hexane, 6.25 mL, 10 mmol) was added to a toluene solution(˜15 mL) of (Me₂N)₂C═NH (1.151 g, 10 mmol) at −78° C. The solution waswarmed to 23° C. in 10 minutes and was further stirred for 30 minutes togive a toluene solution of (Me₂N)₂C═NLi (10 mmol).

The above solution was added to a toluene solution (˜50 mL) of CpTiCl₃(2.19 g, 10 mmol) at −78° C. The mixture was warmed to 23° C. in thecold bath. Yellow precipitate was observed. The slurry was pumped todryness and the residue was extracted with dichloromethane (50 mL). Thedichloromethane solution was filtered and was concentrated to ˜10 mL.The product crystallized at −20° C. as bright orange crystals afterhexane (30 mL) was added. Yield was 2.8 g, 94%. ¹H NMR (toluene-d₈₁δ):6.28 (s, 5H),2.26 (s, 12H).

Synthesis of (^(t)Bu₂C═N)TiCl₂(C₄Me₄P) (where C₄Me₄P istetramethylphospholyl)

^(t)Bu₂C═NLi (0.384 g, 2.610 mmol) in toluene (˜20 mL) was added into atoluene solution (˜30 mL) of (C₄Me₄P)TiCl₃ (0.766 g, 2.610 mmol). Thereaction was warmed to 23° C. in 5 hours. The solution was filtered andthe filtrate was pumped to dryness. The residue was crystallized fromhexane at −70° C. (0.920 g, 96%) as orange crystals. ¹H NMR (toluene-d₈,δ): 2.18 (d, J=9.9 Hz, 6H), 2.03 (s, 6H), 1.17 (s, 18H).

Synthesis of (^(t)Bu₂C═N)TiMe₂(C₄Me₄P)

This compound was prepared as orange crystals in quantitative yield fromthe reaction of (^(t)Bu₂C═N)TiCl₂(C₄Me₄P) and excess of MeMgBr(Procedure was similar to that for the preparation of(^(t)Bu₂C═N)TiMe₂Cp). ¹H NMR (toluene-d₈, δ): 2.02 (d, J=10 Hz, 6H),1.94 (s, 6H), 0.55 (d, J=0.95 Hz, 6H).

Synthesis of [Ph(Me)C═N]TiMe₂Cp (where Ph is phenyl; Me is methyl)

MeLi (1.4 M in ether, 7.14 mL, 10 mmol) was added to PhCN (1.03 g, 10mmol) in ether (−30 mL) at −100° C. The solution was warmed to 23° C. in0.5 hr and was stirred for another 0.5 hours. An orange solution ofPh(Me)C═NLi formed.

The above solution was added to a solution of CpTiCl₃ in ether (˜100 mL)at −78° C. and the reaction mixture was warmed to 23° C. in ˜1 hour. Theorange solution was pumped to dryness and the residue was extracted withtoluene. The toluene solution was filtered and was concentrated to ˜2mL. The product crystallized from a mixture of toluene and hexane at−70° C. Yield 2.93, 97%. ¹H NMR (toluene-d₈, δ): 6.9-7.6 (m, 5H), 6.14(s, 5H), 1.84 (s, 3H).

Synthesis of (^(t)Bu₂C═N)TiCl₂(Ind) (where Ind is indenyl)

A solution Of ^(t)Bu₂C═NLi (0.332 g, 2.17 mmol) in 30 mL of toluene wasadded dropwise to IndTiCl₃ (0,584 g, 2.17 mmol) in 30 mL of toluene at−78° C. Once the addition was complete the solution was allowed to reachroom temperature while being stirred for 16 hours. The purple solutionwas then filtered to remove LiCl and toluene was removed under reducedpressure to give a dark purple crystalline solid. Isolated yield is0.681 g (83%). ¹H NMR (toluene-d₈, δ) (C₇D₈): 7.25 (m, 2H), 6.88 (m,2H), 6.44 (m, 3H), 1.01 (s, 18H). cl Part B: Solution Polymerization

The Continuous Solution Polymerization

All the polymerization experiments described below were conducted on acontinuous solution polymerization reactor. The process is continuous inall feed streams (solvent, monomers and catalyst) and in the removal ofproduct. All feed streams were purified prior to the reactor by contactwith various absorption media to remove catalyst killing impurities suchas water, oxygen and polar materials as is known to those skilled in theart. All components were stored and manipulated under an atmosphere ofpurified nitrogen.

All the examples below were conducted in a reactor of 71.5 cc internalvolume. In each experiment the volumetric feed to the reactor was keptconstant and as a consequence so was the reactor residence time.

The catalyst solutions were pumped to the reactor independently andthere was no pro-contact between the activator and the catalyst. Becauseof the low solubility of the catalysts, activators and MAO incyclohexane, solutions were prepared in purified xylene. The catalystwas activated in-situ (in the polymerization reactor) at the reactiontemperature in the presence of the monomers. The polymerizations wereCarried out in cyclohexane at a pressure of 1500 psi. Ethylene wassupplied to the reactor by a calibrated thermal mass flow meter and wasdissolved in the reaction solvent prior to the polymerization reactor.If commoner (for example 1-octene) was used it was also premixed withthe ethylene before entering the polymerization reactor. Under theseconditions the ethylene conversion is a dependent variable controlled bythe catalyst concentration, reaction temperature and catalyst activity,etc.

The internal reactor temperature is monitored by a thermocouple in thepolymerization medium and can be controlled at the required set point to+/−0.5° C. Downstream of the reactor the pressure was reduced from thereaction pressure (1500 psi) to atmospheric. The solid polymer was thenrecovered as a slurry in the condensed solvent and was dried byevaporation before analysis.

The ethylene conversion was determined by a dedicated on line gaschromatograph by reference to propane which was used as an internalstandard, The average polymerization rate constant was calculated basedon the reactor hold-up time, the catalyst concentration in the reactorand the ethylene conversion and is expressed in l/(mmol*min).

Average polymerization rate (kp)=(Q/(100−Q))×(1/[M])×(1/HUT):

where: Q is the percent ethylene conversion;

[M] is the catalyst (metad concentration in the reactor expressed in mM;and

HUT is the reactor hold-up time in minutes.

EXAMPLE 1

(^(t)Bu₂C═N)TiCl₂Cp was added to the reactor at 37×10⁻⁶ mol/l along withMAO (PMAO-IP, Akzo-Nobel) at Al/Ti=200. [Note: all Al/Ti ratios referredto in the Examples are mol/mol basis)]. The reaction temperature was160° C. and 2.1 gram/min. of ethylene was continuously added to thereactor. An ethylene conversion of 37.5% was observed (see Table 1).

EXAMPLE 2

(^(t)Bu₂C═N)TiCl₂Cp was added to the reactor at 37×10⁻⁶ mol/l along withMAO (PMAO-IP, Akzo-Nobel) at Al/Ti=200 (mol/mol). The reactiontemperature was 160° C., 2.1 gram/min. of ethylene and 4.0 ml/min. of1-octene was continuously added to the reactor. An ethylene conversionof 28.5% was observed (see Table 1).

EXAMPLE 3

(^(t)Bu₂C═N)TiMe₂Cp was added to the reactor at 37×10⁻⁶ mol/l along withPh₃CB(C₆F₅)₄ (Asahi Glass) at B/Ti=1.0 (mol/mol). The reactiontemperature was 160° C. and 2.1 gram/min. of ethylene was continuouslyadded to the reactor. An ethylene conversion of 58.7% was observed (seeTable 1).

EXAMPLE 4

(^(t)Bu₂C═N)TiMe₂Cp was added to the reactor at 18.5×10⁻⁶ mol/l alongwith Ph₃CB(C₆F₅)₄ (Asahi Glass) at B/Ti=1.0 (mol/mol). The reactiontemperature was 160° C. and 2.1 gram/min. of ethylene was continuouslyadded to the reactor. An ethylene conversion of 51.6% was observed (seeTable 1).

EXAMPLE 5

(^(t)Bu₂C═N)TiMe₂Cp was added to the reactor at 37×10⁻⁶ mol/l along withPh₃CB(C₆F₅)₄ (Asahi Glass) at B/Ti=1.0 (mol/mol). The reactiontemperature was 160° C. and 2.1 gram/min. of ethylene along with 4.0ml/min. of purified 1-octene was continuously added to the reactor. Anethylene conversion of 45.5% was observed (see Table 1).

EXAMPLE 6

(^(t)Bu₂C═N)TiCl₂Cp* was added to the reactor at 37×10⁻⁶ mol/l alongwith MAO (PMAO-IP, Akzo-Nobel) at Al/Ti=200 (mol/mol). The reactiontemperature was 160° C. and 2.1 gram/min. of ethylene was continuouslyadded to the reactor. An ethylene conversion of 78.7% was observed (seeTable 1).

EXAMPLE 7

(^(t)Bu₂C═N)TiCl₂Cp* was added to the reactor at 37×10⁻⁶ mol/l alongwith MAO (PMAO-IP, Akzo-Nobel) at Al/Ti=200 (mol/mol). The reactiontemperature was 160° C., 2.1 gram/min. of ethylene and 4.0 ml/min. of1-octene was continuously added to the reactor. An ethylene conversionof 60.3% was observed (see Table 1).

EXAMPLE 8

(^(t)Bu₂C═N)TiCl₂Cp* was added to the reactor at 37×10⁻⁶ mol/l alongwith MAO (PMAO-IP, Akzo-Nobel) at Al/Ti=200 (mol/mol). The reactiontemperature was 160° C., 2.1 gram/min. of ethylene along with 2.0ml/min. of purified 1-octene was continuously added to the reactor. Anethylene conversion of 66.9% was observed (see Table 1).

EXAMPLE 9

(^(t)Bu₂C═N)TiMe₂Cp* was added to the reactor at 37×10⁻⁶ mol/l alongwith Ph₃CB(C₆F₅)₄ (Asahi Glass) at B/Ti=1.0 (mol/mol). The reactiontemperature was 160° C., 2.1 gram/min. of ethylene was continuouslyadded to the reactor. An ethylene conversion of 81.4% was observed (seeTable 1).

EXAMPLE 10

(^(t)Bu₂C═N)TiMe₂Cp* was added to the reactor at 37×10⁻⁶ mol/l alongwith Ph₃CB(C₆F₅)₄ (Asahi Glass) at B/Ti=1.0 (mol/mol). The reactiontemperature was 160° C., 2.1 gram/min. of ethylene and 4.0 ml/min. of1-octene was continuously added to the reactor. An ethylene conversionof 60.8% was observed (see Table 1).

EXAMPLE 11

(^(t)Bu₂C═N)TiMe₂Cp* was added to the reactor at 37×10⁻⁶ mol/l alongwith Ph₃CB(C₆F₅)₄ (Asahi Glass) at B/Ti=1.0 (mol/mol). The reactiontemperature was 140° C. 1.0 gram/min. of ethylene was continuously addedto the reactor. An ethylene conversion of 94.3% was observed (see Table1).

EXAMPLE 12

(^(t)BU₂C═N)TiCl₂(C₄Me₄P) was added to the reactor at 37×10⁻⁶ mol/lalong with Ph₃CB(C₆F₅)₄ (Asahi Glass) at B/Ti=1.0 (mol/mol). Thereaction temperature was 160° C., 2.1 gram/min. of ethylene wascontinuously added to the reactor. An ethylene conversion of 34.5% wasobserved (see Table 1).

EXAMPLE 13

(^(t)Bu₂C═N)TiCl(C₄Me₄P) was added to the reactor at 148×10⁻⁶ mol/lalong with Ph₃CB(C₆F₅)₄ (Asahi Glass) at B/Ti=1.0 (mol/mol). Thereaction temperature was 160° C., 2.1 gram/min. of ethylene and 3.0ml/min. of 1-octene was continuously added to the reactor. An ethyleneconversion of 46.1% was observed (see Table 1).

COMPARATIVE EXAMPLE 14

(C₅Me₅)₂ZrCl₂ (purchased from Strem, where C₅Me₅ ispentamethylcyclopentadienyl) was added to the reactor at 37×10⁻⁶ mol/lalong with MMAO-3 (Akzo-Nobel, Al/Ti=400 mol/mol). The reactiontemperature was 140° C. and 1.0 gram/min. of ethylene was continuouslyadded to the reactor. An ethylene conversion of 55.5% was observed (seeTable 1).

COMPARATIVE EXAMPLE 15

(C₅Me₅)₂ZrCl2 (Strem) was added to the reactor at 37×10⁻⁶ mol/l alongwith MMAO-3 (Akzo-Nobel, Al/Ti=400 mol/mol). The reaction temperaturewas 160° C. and 1.0 gram/min. of ethylene was continuously added to thereactor. An ethylene conversion of 35.6% was observed (see Table 1).

COMPARATIVE EXAMPLE 16

(C₅Me₅)₂ZrCl₂ (Strem) was added to the reactor at 37×10⁻⁶ mol/l alongwith MMAO-3 (Akzo-Nobel, Al/Ti=400 mol/mol). The reaction temperaturewas 160° C. and 2.1 gram/min. of ethylene was continuously added to thereactor. An ethylene conversion of 37.4% was observed (see Table 1).

COMPARATIVE EXAMPLE 17

rac-Et(Ind)₂ZrCl₂ ((i.e. raceimic form of ethylene bridged bis indenylZrCl₂, purchase from Witco) was added to the reactor at 37×10⁻⁶ mol/lalong with MMAO-3 (Akzo-Nobel, Al/Ti=400 mol/mol). The reactiontemperature was 160° C. and 2.1 gram/min. of ethylene was continuouslyadded to the reactor. An ethylene conversion of 94.6% was observed (seeTable 1).

COMPARATIVE EXAMPLE 18

rac-Et(Ind)₂ZrCl₂ (Witco) was added to the reactor at 37×10⁻⁶ mol/lalong with MMAO-3 (Akzo-Nobel, Al/Ti=400 mol/mol). The reactiontemperature was 160° C. and 2.1 gram/min. of ethylene and 3.25 ml/min.of 1-octene was continuously added to the reactor. An ethyleneconversion of 94.8% was observed (see Table 1).

EXAMPLE 19 Slurry Polymerization

Slurry polymerizations were carried out in a temperature controlledreactor at 35° C. at an ethylene pressure of 10 psig. 300 ml of purifiedcyclohexane was first transferred to the reactor followed by MAO(PMAO-IP, Akzo-Nobel, 1.8 ml of 12.9 wt % Al) and was then stirred for 5minutes. The catalyst (^(t)Bu₂C═N)TiCl₂Cp (15.2×10⁻⁶ moles, to give areactor concentration of 50×10⁻⁶ M, Al/Ti=500) was then added and thereactor pressurized to 10 psig with ethylene. Polymerization was allowedto continue to 30 minutes at which time the pressure was vented (toprevent further reaction) and the polymer was recovered by evaporationof the solvent. Reactor temperature and ethylene consumption weremonitored during the reaction. The polymer yield was 5.08 g giving anactivity of 0.17 kg PE/(mmol Ti×hr).

EXAMPLE 20 Slurry Polymerization

Reaction conditions were similar to those of example 19. MAO (PMAO-IP,Akzo-Nobel, 1.8 ml of 12.9 wt % Al) and (^(t)Bu₂C═N)TiCl₂Cp* (15.2×10⁻⁶moles, to give a reactor concentration of 50×10⁻⁶ M, Al/Ti=500) wereadded and the reactor pressurized to 10 psig with ethylene. The polymeryield was 6.26 g giving an activity of 0.21 kg PE/(mmol Ti×hr).

EXAMPLE 21 Slurry Polymerization

Reaction conditions were similar to those of example 19. MAO (PMAO-IP,Akzo-Nobel, 1.8 ml of 12.9 wt % Al) and [(Me₂N)₂C═N]TiCl₂Cp (15.2×10⁻⁶moles, to give a reactor concentration of 50×10⁻⁶ M, Al/Ti=500) wereadded and the reactor pressurized to 10 psig with ethylene. The polymeryield was 0.81 g giving an activity of 0.03 kg PE/(mmol Ti×hr).

EXAMPLE 22 Slurry Polymerization

Reaction conditions were similar to those of example 19. MAO (PMAO-IP,Akzo-Nobel, 1.8 ml of 12.9 wt % Al) and (^(t)Bu₂C═N)TiCl₂Ind (15.2×10⁻⁶moles, to give a reactor concentration of 50×10⁻⁶ M, Al/Ti=500) wereadded and the reactor pressurized to 10 psig with ethylene. The polymeryield was 13.02 g giving an activity of 0.43 kg PE/(mmol Ti×hr).

EXAMPLE 23 Slurry Polymerization

Reaction conditions were similar to those of example 19. MAO (PMAO-IP,Akzo-Nobel, 1.8 ml of 12.9 wt % Al) and (^(t)Bu₂C═N)TiCl₂(C₄Me₄P)(15.2×10⁻⁶ moles, to give a reactor concentration of 50×10⁻⁶ M,Al/Ti=500) were added and the reactor pressurized to 10 peig withethylene. The polymer yield was 2.63 g giving an activity of 0.09 kgPE/(mmol Ti×hr).

COMPARATIVE 24 Slurry Polymerization

Reaction conditions were similar to those of example 19. MAO (PMAO-IP,Akzo-Nobel, 1.8 ml of 12.9 wt % Al) and [Ph(Me)C═N]TiMe₂Cp (15.2×10⁻⁶moles, to give a reactor concentration of 50×10⁻⁶ M, Al/Ti=500) wereadded and the reactor pressurized to 10 psig with ethylene. The polymeryield was 0.84 g giving an activity of 0.03 kg PE/(mmol Ti×hr).

COMPARATIVE EXAMPLE 25 Slurry Polymerization

Reaction conditions were similar to those of example 19. MAO (PMAO-IP,Akzo-Nobel, 1.8 ml of 12.9 wt % Al) and Ph₂C(Flu)(Cp)ZrCl₂ (15.2×10⁻⁶moles, to give a reactor concentration of 50×10⁻⁶ M, Al/Ti=500) wereadded and the reactor pressurized to 10 psig with ethylene. The polymeryield was 5.64 g giving an activity of 0.02 kg PE/(mmol Zr×hr).

COMPARATIVE EXAMPLE 26 Slurry Polymerization

Reaction conditions were similar to those of example 19. MAO (PMAO-IP,Akzo-Nobel, 1.8 ml of 12.9 wt % Al) and (Cp)₂ZrCl₂ (15.2×10⁻⁶ moles, togive a reactor concentration of 50×10⁻⁶ M, Al/Ti=500) were added and thereactor pressurized to 10 psig with ethylene. The polymer yield was20.18 g giving an activity of 0.69 kg PE/(mmol Zr×hr).

TABLE 1 Total Calculated Flow To Catalyst Ethylene PolymerizationPolymer Polymer Reactor Concentration Conversion Rate (kp) Density MeltMn × Mw × Example (ml/min.) (mol × 10⁶) (%) (l/mmol × min.) (g/cc) Index10⁻³ 10³  1 27.0 37.0 37.5 6.2 0.958 0.08 52 174  2 27.0 37.0 28.5 4.10.920 0.452 43 128  3 27.0 37.0 58.7 14.5 — — — —  4 27.0 18.0 51.6 21.80.9371 21 0.001 227 448  5 27.0 37.0 45.5 8.5 0.8965 0.003 — —  6 27.037.0 78.7 37.7 0.951 0.04 113 218  7 27.0 37.0 60.3 15.5 0.906 0.078 77184  8 27.0 37.0 66.9 20.6 0.913 0.042 — —  9 27.0 37.0 81.4 44.7 — — —— 10 27.0 37.0 60.8 15.8 0.8868 0.100 — — 11 27.0 37.0 94.3 169.6 0.9420.023 — — 12 27.0 37.0 34.5 5.4 — — — — 13 27.0 148.1 46.1 2.2 0.9060.007 63 288 14 27.0 37.0 55.5 12.7 — 880 2.7 10.0 15 27.0 37.0 35.6 5.6— — 1.8 7.5 16 27.0 37.0 37.4 6.1 — 620 3.3 12.0 17 27.0 37.0 94.6 178.6— 1300 3.9 14.0 18 27.0 37.0 94.8 186.0 0.925 very high 2.6 10.0

Part C: Gas Phase Polymerization

Catalyst Preparation and Polymerization Testing Using a Semi-Batch, GasPhase Reactor

The catalyst preparation methods described below employ typicaltechniques for the syntheses and handling of air-sensitive materials.Standard Schlenk and drybox techniques were used in the preparation ofligands, metal complexes, support substrates and supported catalystsystems. Solvents were purchased as anhydrous materials and furthertreated to remove oxygen and polar impurities by contact with acombination of activated alumina, molecular sieves and copper oxide onsilica/alumina, Where appropriate, elemental compositions of thesupported catalysts were measured by Neutron Activation analysis and areported accuracy of ±1% (weight basis).

The supported catalysts were prepared by initially supporting MAO on asilica support, followed by deposition of the catalyst component.

All the polymerization experiments described below were conducted usinga semi-batch, gas phase polymerization reactor of total internal volumeof 2.2 L. Reaction gas mixtures, including separately ethylene orethylene/butene mixtures were measured to the reactor on a continuousbasis using a calibrated thermal mass flow meter, following passagethrough purification media as described above. A pre-determined mass ofthe catalyst sample as added to the reactor under the flow of the inletgas with no pre-contact of the catalyst with any reagent, such as acatalyst activator The catalyst was activated in-situ (in thepolymerization reactor) at the reaction temperature in the presence ofthe monomers, using a metal alkyl complex which has been previouslyadded to the reactor to remove adventitious impurities. Purified andrigorously anhydrous sodium chloride was used as a catalyst dispersingagent.

The internal reactor temperature is monitored by a thermocouple in thepolymerization medium and can be controlled at the required set point to+/−1.0° C. The duration of the polymerization experiment was one hour.Following the completion of the polymerization experiment, the polymerwas separated from the sodium chloride and the yield determined.

Table 2 illustrates data concerning the Al/transition metal ratios ofthe supported catalyst; polymer yield and polymer properties.

TABLE 2 Support¹ mg of Homo² Yield g Pe³/g g Pe³/g Al/Ti Complex mmolComplex (g) Catalyst or Co² (g) Metal Catalyst Ratio (^(t)Bu₂C═N)TiCl₂Cp52 mg (160 mmol) 1.485 48 Homo 2.6 5710 54 86.00 51 Co 1.7 3514 33(^(t)Bu₂C═N)TiCl₂Cp* 45 mg (114 mmol) 1.031 18 Homo 13.8 76405 767 68.2425 Co 2.4 89295 896 (^(t)Bu₂C═N)TiCl₂Ind 44 mg (118 mmol) 1.012 26 Homo10.9 41404 419 79.47 31 Co 11.4 36319 368 (^(t)Bu₂C═N)TiCl₂(C₄Me₄P) 44mg (110 mmol) 0.999 33 Homo 1 3134 30 84.15 29 Co 0.6 2140 21 ¹Supportis Witco/MAO SiO₂ TA 02794/HL/04 ²Ethylene homopolymerization (Homo) orEthylene-Butene copolymerization (Co) ³Pe = Polyethylene

What is claimed is:
 1. A catalyst system for olefin polymerizationcomprising: a) a catalyst which is an organometallic complex of a group4 metal; and b) an activator, characterized in that such organometalliccomplex contains a ketimide ligand.
 2. The catalyst system according toclaim 1 wherein said organometallic complex further contains a cyclicligand which forms a delocalized pi-bond with said group 4 metal.
 3. Thecatalyst system according to claim 1 wherein said organometallic complexis defined by the formula: (L₁)(L₂)M(X)₂ wherein M is a metal selectedfrom Ti, Hf and Zr; L₁ is a ketimide ligand; L₂ is a delocalized cyclicligand which forms a pi-bond with said M and each X is a non-interferingligand.
 4. The catalyst system according to claim 3 wherein L₂ is acyclopentadienyl-type ligand and each X is independently selected fromhalogen, hydrogen, hydrocarbyl having up to 10 carbon atoms, amido andphosphido.
 5. The catalyst system according to claim 3 wherein saidorganometallic complex is defined by the formula:

wherein: said M is selected from Ti and Zr; said Cp is acyclopentadienyl-type ligand; each of said X is a non-interferingligand; and each of said Sub 1 and Sub 2 is independently selected fromhydrocarbyls having from 1 to 20 carbon atoms, silyl groups, amidogroups and phosphido groups.
 6. The catalyst system according to claim5, wherein said M is titanium, said Cp is a cyclopentadienyl ligand,each of said Sub 1 and Sub 2 is a tertiary butyl group and each of saidX is selected from halogen and methyl.
 7. The catalyst system accordingto claim 1 wherein said activator is an alumoxane.
 8. The catalystsystem according to claim 1 in support form.
 9. The catalyst systemaccording to claim 1 wherein said activator is methalumoxane and whereinsaid support is selected from the group consisting of silica,silica-alumina and alumina.
 10. The catalyst system according to claim 1in homogeneous form.
 11. The catalyst system according to claim 10wherein said activator comprises a substantially non coordinating anion.